Add new API GetTimeInNanoSecond() to TimerLib to convert elapsed ticks to time in...

[mirror_edk2.git] / MdePkg / Library / SecPeiDxeTimerLibCpu / X86TimerLib.c

diff --git a/MdePkg/Library/SecPeiDxeTimerLibCpu/X86TimerLib.c b/MdePkg/Library/SecPeiDxeTimerLibCpu/X86TimerLib.c
index 6d4b0938e9de6ee345e891ef820ddca97b8a3a5a..ffd6cc27145c77eaedbf3981608ec85ed4a73824 100644 (file)
--- a/MdePkg/Library/SecPeiDxeTimerLibCpu/X86TimerLib.c
+++ b/MdePkg/Library/SecPeiDxeTimerLibCpu/X86TimerLib.c
@@ -1,7 +1,7 @@
 /** @file\r
   Timer Library functions built upon local APIC on IA32/x64.\r
 \r
-  Copyright (c) 2006 - 2008, Intel Corporation. All rights reserved.<BR>\r
+  Copyright (c) 2006 - 2011, Intel Corporation. All rights reserved.<BR>\r
   This program and the accompanying materials\r
   are licensed and made available under the terms and conditions of the BSD License\r
   which accompanies this distribution.  The full text of the license may be found at\r
@@ -255,3 +255,47 @@ GetPerformanceCounterProperties (
 \r
   return (UINT64) InternalX86GetTimerFrequency (ApicBase);\r
 }\r
+\r
+/**\r
+  Converts elapsed ticks of performance counter to time in nanoseconds.\r
+\r
+  This function converts the elapsed ticks of running performance counter to\r
+  time value in unit of nanoseconds.\r
+\r
+  @param  Ticks     The number of elapsed ticks of running performance counter.\r
+\r
+  @return The elapsed time in nanoseconds.\r
+\r
+**/\r
+UINT64\r
+EFIAPI\r
+GetTimeInNanoSecond (\r
+  IN      UINT64                     Ticks\r
+  )\r
+{\r
+  UINT64  Frequency;\r
+  UINT64  NanoSeconds;\r
+  UINT64  Remainder;\r
+  INTN    Shift;\r
+\r
+  Frequency = GetPerformanceCounterProperties (NULL, NULL);\r
+\r
+  //\r
+  //          Ticks\r
+  // Time = --------- x 1,000,000,000\r
+  //        Frequency\r
+  //\r
+  NanoSeconds = MultU64x32 (DivU64x64Remainder (Ticks, Frequency, &Remainder), 1000000000u);\r
+\r
+  //\r
+  // Ensure (Remainder * 1,000,000,000) will not overflow 64-bit.\r
+  // Since 2^29 < 1,000,000,000 = 0x3B9ACA00 < 2^30, Remainder should < 2^(64-30) = 2^34,\r
+  // i.e. highest bit set in Remainder should <= 33.\r
+  //\r
+  Shift = MAX (0, HighBitSet64 (Remainder) - 33);\r
+  Remainder = RShiftU64 (Remainder, (UINTN) Shift);\r
+  Frequency = RShiftU64 (Frequency, (UINTN) Shift);\r
+  NanoSeconds += DivU64x64Remainder (MultU64x32 (Remainder, 1000000000u), Frequency, NULL);\r
+\r
+  return NanoSeconds;\r
+}\r